code: def test_fit_seq():
      """[Sequential] Test multilayer fitting."""
      S = lc_s.fit_transform(X, y)
      B = lc_b.fit_transform(S, y)
      r = y.shape[0] - B.shape[0]
      U = lc_u.fit_transform(B, y[r:])
      out = seq.fit_transform(X, y)
      np.testing.assert_array_equal(U, out)
  
file_path: mlens/mlens/ensemble/tests/test_sequential.py
imports: import numpy
  from mlens.ensemble import SequentialEnsemble, SuperLearner, BlendEnsemble, Subsemble
  from mlens.ensemble.base import Sequential
  from mlens.testing.dummy import Data, PREPROCESSING, ESTIMATORS, ECM, EstimatorContainer
label_desc: Use image node_id 1 for calling a global function with example usage: test_fit_seq() without return types